logto-io Logto up to 1.40.x TOTP Verifier authentication replay

Summaryinfo

A vulnerability categorized as critical has been discovered in logto-io Logto up to 1.40.x. Impacted is an unknown function of the component TOTP Verifier. Executing a manipulation can lead to authentication replay. This vulnerability is tracked as CVE-2026-55370. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in logto-io Logto up to 1.40.x. It has been declared as critical. This vulnerability affects an unknown functionality of the component TOTP Verifier. The manipulation with an unknown input leads to a authentication replay vulnerability. The CWE definition for the vulnerability is CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Logto is the modern, open-source auth infrastructure for SaaS and AI apps. Prior to 1.41.0, Logto's existing TOTP verification accepted a successfully used TOTP code again while the code remained inside the RFC 6238 acceptance window because the verifier used otplib's stateless check with window = 1 and did not persist or compare the accepted TOTP time-step counter. An attacker who has the victim's first factor and captures a live TOTP value can replay that value to satisfy MFA during the same acceptance window. This issue is fixed in version 1.41.0.

The advisory is available at github.com. This vulnerability was named CVE-2026-55370 since 06/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1040 by the MITRE ATT&CK project.

Upgrading to version 1.41.0 eliminates this vulnerability.

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Productinfo

Vendor

• logto-io

Name

• Logto

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 1.30
• 1.31
• 1.32
• 1.33
• 1.34
• 1.35
• 1.36
• 1.37
• 1.38
• 1.39
• 1.40

Website

• Product: https://github.com/logto-io/logto/

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